On the left are a series of power measurements I made on the Celluon PicoPro projector with an optical engine designed by Sony using a Microvision scanning mirror. The power was calculated based on the voltage and current from current coming from the battery using the HDMI input.

The first 6 measurements were with a solid image of the black/white/color indicated. For the last 3 measurements I did an image that was half black on the left and the other half white, an image that was top half black, and a screen of 1 pixel wide vertical stripes. The reason for the various colors/patterns was to gain some additional insight into the power consumption (and will be covered in a future article). In addition to the power (in Watts) added a column with the delta power from the Black image.

Picture of Celluon PicoPro Battery

The Celluon PicoPro consumes 2.57 Watts for a fully black image (there are color lines at the bottom, presumably for laser brightness calibration) and 6.14W for a 32 lumen full white image. When you consider that a smart phone running with the GPS only consumes about 2.5W and a smart phone LCD on full brightness consumes about 1W to 1.5W, over 6W is a lot of power (Displaymate has and excellent article on smartphone displays that includes the power consumption). The Celluon has a 3260mah / 12.3Wh battery which is bigger than what goes in even large smartphones (and fills most of the left side of the case).

So why does the Celluon unit not need a fan, the answer is A) it only outputs 32-lumens and B) it use a lot of thermal management build into the case to spread the heat from the projector. In the picture below I have shown some of the key aspects of the thermal management. I have flipped over the projector and indicated with dashed rectangles were the thermal pads (a light blue color) go to the projector unit. In addition the cast aluminum body used to hold the lasers and the optics which acts as a heat sink to spread the heat, there is gray flexible heat spreading material lining the entire top and bottom of the case plus a more hidden, a heat sink amalgamation essentially dedicated to the lasers as well as aluminum fins around the sides of the case.

The heat spreading material on the left (as view) top of the case is pretty much dedicated to the battery, but all the rest of the heat spreading, particularly along the bottom of the case goes to the projector.

The most interesting feature is that there is a dedicated heat path from the area where the lasers are held in the cast body to the a heat sink “hidden chamber” or what I have nicknamed “the thermal corset”. You should notice that there are three (3) light blue heat pads on the right side of the case top and that the middle one is isolated from the other two. This middle one is also thicker and goes through a hole in the main case body to a chamber that filled with a heat sink material and then covered with an outer case. This also explains why the Cellouon unit looks like it is in two parts from the outside.

Don’t get me wrong, having a fanless projector is desirable, but it is not due to the “magic” of using lasers. Quite to the contrary, the Celluon unit has comparitively poor lumens per Watt, about double the power of what a similar DLP projector would take for the same lumens.

You may want to notice in the table that if you add up the “delta” red, green, and blue it totals to a lot more than the delta white. The reason for this is that the Celluon unit never puts out “pure” fully saturated primary colors. It always mixes a significant amount of the other two colors (I have verified this with several methods including using color filters over the output and using a spectral-meter). This has to be done (and is done with LED projectors as well) so that the colors called for by standard movies and pictures are not over-saturated (if you don’t do this, green grass, for example” will look like it is glowing).

Another interesting result is that the device consumes more power if I put up a pattern were the left half is black and the right half is white rather than having the top half black and the bottom half white. This probably has something to do with laser heating and not getting a chance to cool down between lines.

I also put up a pattern with alternating 1 pixel wide vertical lines and it should be noted that the power is between that of the left/right half screen image and the full white image.

So what does this mean in actual use? With “typical” movie content, the image is typically about 25% to 33% (depends on the movie) of full white so the projector will be consuming about 4 Watts per hour which with a 12.3Wh battery will go about 3 hours. But if you are web browsing, the content is often more like 90% of full white so it will be consuming over 6W per hour or 4 to 6 times what a typical smartphone displays consumes. Note this is before you add in the power consumed in getting and processing the data (say from the internet).

Conclusion

The Celluon projector may be fanless, but not because it is efficient. From a product perspective, it does do a good job with its “thermal corset” of hiding/managing the power.

This study works from the “top down” by measuring the power and seeing where the heat is going in the case, the next time I plan to work some “bottom’s up” numbers to help show what causes the high power consumption and how it might change in the future.

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19 comments

Very interesting read, Karl. Sounds like the Microvision/Sony engineers have their work cutout if they want to compete with the power efficiencies of panel based projectors (LCOS, DLP, etc.). This is somewhat disappointing to me, since the mirror actuated, laser-based projectors have been on the market for about 5+ years now. I was hoping for more progress with power efficiency.

I look forward to your “bottom’s up” numbers. I’m curious about components that are needlessly hogging power (mirror actuator, signal processing, lasers)? My guess is it’s simply the components that create the most waste heat in the “big thermo corset.”

Microvision/LBS has improved over 6 years ago (the ShowWX) but they were very far behind everything. Today they are about 2X to 3X behind DLP in lumens/Watt (depends on what “counts” in the power computations).

Taking 2W just to put up black is a major problem. Then you have direct green lasers only having about a 6% “wall plug efficiency” (WPE, or electrical to light power conversion) which works our for a 522nm wavelength of only about 30.4 lumens per Watt whereas a OSRAM green phosphor converted (blue LED with a green phosphor) LED commonly used in DLP projectors has about 250 lumens per Watt. Thus for the same power to the diode, the DLP starts with 8X more lumens.

Another significant loss with the laser scanning is that there are additional significant losses in the high speed laser control (note the laser’s light output has to be able to change on a pixel by pixel basis). Rough calculations show that the MVIS system power for the lasers is about 1.5X higher due to these losses. Will green Lasers get better, certainly, but it is likely to take a long time as they are hard to make and there is not a large market for them and there will still be bigger losses in the high speed linear (light level) control of the lasers.

It seems doubtful to me that the Sony device (assuming it goes to market this year) will be significantly different in terms of efficiency than the Celluon unit. I would expect them to be using the same or very similar engine.

They may or may not add “digital” keystone correction as that would not be that difficult. But digital keystone correction comes at a further loss in resolution (basically you are just incrementally scaling down the image on a line by line basis to make them cover the same area).

My PicoPro user manual stated that the capacity of the battery is 3140 mAh and many reviewers testified that they can watch movie/video for 3+ hours.

OTOH, the LCoS based UO Smart Beam laser pico projector recently advertised on Amazon listed its battery capacity as 4200 mAh (1.34 times of that of PicoPro) yet the playing time is listed as 2 hours (0.67 of that of PicoPro). That means UO Smart Beam laser projector consumes twice as much power or more as PicoPro.

Is this higher power requirement in UO Smart Beam inherent in the LCoS technology, or is it due to poor engineering implementation of the end product? I understand that part of the power is consumed for running the cooling fan.

You appear to have ignored that the UO Smart Beam is listed as having 50 lumens (I have not measured it) or 1.56X the lumens of the PicoPro. For an LBS projector the run time will vary greatly depending on content as I pointed out in the article. It will consume between 2.5W and 6.14W based on the content. A “panel display,” ala the UO Projector, unless it does dimming based on content is going to consume about the same regardless of the scene brightness.

So at least on the surface spec’s (unverified), the UO has more lumens per Watt. It could be that the PicoPro will have more run time with movie content (typical content has pixels that average only about 25% to 33% of “white). I don’t know if the UO has “dynamic dimming” that would improve the run time with movies or not (I would suspect it does not or they would make a point of it).

The Celluon PicoPro is on the edge of needing a fan as well. If it could put out 1.5X the lumens it would either need a much bigger case to accommodate more heat sinking or a fan. I measured the temperature of the cast body for the PicoPro lasers and at full brightness they were getting to 60C which is the spec limit for most of the lasers available.

The projector is efficient as laser light looks brighter(50%+) for the same lumen rating than with LED. This means this projector is equivalent to a 50 to 60 lumen LED projector. Comparing power usage to smartphone displays makes no sense as this outputs a greater amount light. In the projector there is a motor which changes the angle of the mirror which is needed because it only projects one pixel at a time but the mirror changes where the pixel is on the screen so it moves the pixel all 1920 poxitions and then to the next row(there are a total of 720 rows) it is this motor that consumes a lot of power and not the lasers themselves.

It is simply a LIE that “laser lumens” look brighter than “LED Lumens.” This lie has been repeated many time by Microvison, but that does not make it true (it is a lie/falsehood). Go find any serious/independent study that shows this (good luck you will not).

You obviously don’t have a clue as to where the power is consumed, I would suggest you read my blog articles on the subject more carefully. The power of the mirror movement is only a very small part of the power consumed.

What counts is whether the image is resolvable at the stated resolution. By any objective measure the so call 1920×720 resolution has the same effective resolution of about a 640 by 360 resolution display. I has published many pictures proving this.

You say the resolution is about 640 by 360 but how are you measuring this? If you haven’t already you could measure the width of the projected image and the width of 1 pixel and use that to work out the resolution (if you haven’t already).
I have read this article but could you please tell me what you are saying is using most of the power?
As for laser lumens looking brighter than LED lumens you might be right but I got some information from a link( below) and I wondered what you would say about it?
“What’s this deal with the lumens rating and lasers?
If you’ve ever used a laser pointer, you know that the resultant dot is very bright, but the light is mostly isolated to the area of that dot. The point does not create much ambient light reflection all over the room. A flashlight, on the other hand, will have a lot of ambient light bouncing around, illuminating things that are outside of the beam of light.
Link: http://www.uobeam.com/frequently-asked-questions.html
“The ANSI (American National Standards Institute) lumens test is a very specific test designed to accurately measure the light output by looking at the amount of light reflected off a screen. It’s a great gauge of brightness for typical bulb-type projectors, but since it measures the reflection of light, it does not translate well for lasers . This means that even though we’ve put a competent 60 lumens into such a small package, it will seem far brighter than an LED projector of similar lumens!”

Thanks for blogging! It is very informative and useful! I’ve been reading your blog for days!

There is one issue when you use lasers as a light source, the specklling. In HMD environment, a vibrating despeckler is very annoying. Instead, small, light, static despecklers and other means for despeckling is necessary.

Do you know how, say Microsoft Hololens and other big players, despecklling? I saw you mentioned this topic briefly for general pico projectors. But I hope you can talk about it more in details please.

I don’t know of anyone seriously using lasers in a head mount display (there might be the odd experimental system).

Microsoft’s Hololoens has nothing to do with lasers or even holograms. It uses LCOS (reportedly by Himax) and LEDs for illumination. They have “appropriated” the word “hologram” with their own new marketing based definition (as in it has nothing to holograms as they were previously known). What Microsoft is now calling a hologram is where you combine depth information with a computer generated object, depth information within the “real world” and then show it with binocular 3-D stereo to a persons eyes. So it is not a hologram in the scientific sense where the image generation requires lasers.

Thanks Karl! I tried the Hololens briefly the other days. It seemed that it is only suitable for in door use as it needs to map the environment first. Also the brightness is still not good enough for bright day out door activities. So I though Laser based pico projector must be the next logical and natural step for a head mount display. From my very limited knowledge, quiet despeckller is a fator holding it back. Do you think there are other reasons? AR + Laser based pico projector is the best combination for some practical applications. Hope you can talk about this at some point. Best.

LCOS with LEDs can achieve very high levels brightness (nits) in near eye applications, lasers have nothing to do with the brightness limits. Laser can definitely help projectors due to their etendue/f-number characteristics and there are serious efforts to use them projectors. With a projector only an extremely small percentage of the light that is projected will reflect/scatter off a screen and make it a given eye whereas with near eye a high percentage of the light makes it to the eye. So while LEDs light will be less efficiently collected than laser light, LEDs are so much less expensive and easier to control that lasers just aren’t necessary. So it was a simply a design decision on how bright to make the display on Microsoft’s part. A somewhat brighter LED could give off more than enough light for outdoor use without requiring the complexity and cost of using lasers.

As far as outdoor use goes, probably a much bigger limiting factor is the “mapping” of the environment. Most of these mapping techniques use infrared illumination that would be flooded out by the huge amount of IR in sunlight; effective the sun will blind all the IR sensors. The unpredictability and changing of the illumination by the sun (it moves over time, clouds go by, fluttering leaves, etc.) further complicates matters. It would be illegal/dangerous to put out enough IR to compete with the sunlight to make the mapping/gesture work. I always found it funny when gesture recognition companies brag that their stuff will work in total darkness which is the easiest case, sunlight is the worst case. So the ability to Map/Track is a much bigger limiting factor than brightness of the visible display.

Lasers can and will be used with front projection to illuminate a panel such as DLP or LCOS, in fact, there is an industry consortium call LIPA (laser illuminated projector association). It looks likely that eventually all front projector will use laser illumination of panels. The advantages of low f-number light for smaller/less expensive optics with the longer lifetime of lasers compared to bulbs will cause them eventually take over. Additionally the fact that laser light is usually highly polarized could given them an added advantage in 3-D applications.

Two Tree Photonics that developed the holographic HUD has been acquired and I have not heard anything past the original announcement so I don’t know how it has fared. Note that the digital holograms are only a means to an end that still results in an essentially flat 2-D image not say a 3-D hologram. Frankly I don’t understand how this method could be cost effective when compared to other techniques and think it may have been adopted more for the “marketing splash”.

99.9999+% of all things called holograms are NOT holograms (including Hololens) but the term “hologram” is used because it sounds high tech. Most things are just “Pepper’s Ghost” effects off a glass or clear plastic surface.

Real time 3-D holograms are still a thing of science fiction (at least at any decent resolution). Light Field Displays are an approximation that piece wise generate depth; the problem is they generally need on the over of 10 to 30 times the information content available to the eye at one time and thus the cost and power goes up dramatically which in turn is a big problem for making a practical HMD. Nvidia has put out some good papers (example https://research.nvidia.com/sites/default/files/publications/NVIDIA-NELD_0.pdf ) on the subject and reportedly light field displays are being used by Magic Leap (the startup “Unicorn” that has raised over $1B). Personally I don’t see how light field displays are going to make it into a practical AR/VR system until at least 10 years after we see the wide adoption of HMD (which is still a ways off).

I bought a PicoPro about 18 months ago, used once for a presentation, then tried again last week, to find that the battery would charge, indicator lights functioned, but the laser would not shine or create a display. I called Celluon, and was told that after 1 year warranty, a nonfunctioning unit must be thrown away, as there is no support, no repair, and no schematics available for reference. In fact, I was referenced to this site and your review, which apparently contains the only topical discretion of the units innards! I opened it up and checked basic cable connections, but that is about all I could do. I certainly do not recommend this unit, unless intended for short-term use.

Sorry to hear about your troubles. Unfortunately, most small electronics today are not designed to be repaired (this is not unique to Celluon). If you send it back under warranty they might try to debug it to figure out what when wrong and then would swap the board(s) out or just sent you a new unit (rather than put labor into fixing it). If you had two of them you might be able to isolate it by swapping boards/connectors around but it still might be something that cannot be repaired. Unless it is simple like the battery, you are probably out of luck.

I’m curious about your “use case” as in why did you buy the unit, use it once, and then not use it for 18 months? After all it was essentially free and available. So why didn’t you keep it with you (much/all the time) and use it? I suspect you found that it was not all that practical/useful per an article I wrote back in 2013 (http://www.kguttag.com/2013/08/04/whatever-happened-to-pico-projectors-embedding-in-phones/). I’m guessing the first time you brought it out it was impressive, but then you didn’t find you regularly had the “right” conditions to use it.

I’m also curious whether being “focus free” was all that important; in most real world application, you set up the projector and focus it once and you are done, just not a big deal compared to the issues of lighting, having a place to project onto that is decent, and a place to put the projector.